If the degree of operating leverage is 4, then a one percent change in quantity sold should result in a four percent change in:

A) unit contribution margin.
B) revenue.
C) variable expense.
D) net operating income.

Degree of operating leverage (DOL) is defined as the percentage change in net operating income (NOI) divided by the percentage change in quantity sold. In this case, a DOL of 4 means that a 1% change in quantity sold should result in a 4% change in NOI. Therefore, the correct answer is D- net operating income.